Medications are the most commonly used form of medical therapy and yet the single most frequent cause of adverse events. Many of these adverse events are caused by medication errors, and a large proportion of these errors occur in the dispensing, transcribing and administration stages of the medication use process. While the use of barcode technology in conjunction with an electronic medication administration record system has been proposed as a promising way to reduce medication errors, its ability to reduce medication errors, its acceptance by staff, and its cost-benefit ratio remain unclear. Without clear-cut evidence to clarify these issues. It is not clear how health care organizations would prioritize this technology among the many safety interventions. The applicant therefore proposes to answer three related questions in this study: 1) How effective is barcode and electronic medication administration record (barcode/eMAR) technology at reducing medication errors in hospitalized patients? 2) What is the impact of barcode/eMAR technology on nursing and pharmacy efficiency and satisfaction? 3) Can the cost of barcode/eMAR technology be justified by its benefits? The Brigham and Women's Hospital (BWH) is in an excellent position to answer these questions using rigorous methodologies. As part of a multi-disciplinary patient safety initiative, the BWH has committed 3 million dollars to build a state-of-the-art barcode/eMAR system. This system has also been designed to enhance the workflow of nurses and pharmacists during the medication use process. In addition, the research team has substantial prior expertise in conducting rigorous medication error research studies. In this 24-month study, the applicant will leverage these resources to conduct a randomized controlled trial to examine the impact of barcode/eMAR technology on medication transcribing and administration errors. The applicant will also conduct a before-and-after trial to examine its impact on pharmacy dispensing errors. Nursing and pharmacy efficiency will be assessed with time-motion studies, and staff satisfaction will be assessed using validated survey instruments. The applicant will also perform a cost-benefit analysis from the hospital and societal perspectives so that other hospitals and policy makers will be better informed as they consider implementing similar systems. The applicant believes that this study will advance the national patient safety agenda and significantly impact the way medication is delivered by hospitals in the future.